LAX94LA114

While in cruise, the pilot noticed that his engine began running roughly. He made a precautionary landing at a nearby airport, but was unable to identify the problem. A second ground run-up developed only 2,100 rpm's at full throttle. He then called the operator. After a discussion, he decided that if the engine performance improved, he would fly back. On the next run-up, the rpm improved in the 2,200-to-2,300 rpm range, and the pilot felt this was fine for takeoff. The takeoff roll seemed slower than normal, so he decided to climb over the airport in case of an emergency. On climbout at 100-to-200 feet agl, the engine again began running roughly. He began a shallow turn back toward the runway, and lost control of the aircraft. The aircraft stalled, impacted the ground, and nosed over. An inspection of the engine showed the rocker arm boss on the No. 1 cylinder had fractured due to fatigue cracking. Lab analysis showed the boss was welded during cylinder overhaul, a procedure not allowed by Continental.

On February 6, 1994, at 1528 Pacific standard time, a Cessna 150F, N8855S, lost engine power during the takeoff initial climb at Borrego Springs, California. The pilot lost control of the aircraft during an attempted return to airport maneuver and crashed short of the runway. The aircraft was owned and operated by Plus One Flyer's, Inc., of San Diego, California, and had been rented by the pilot for a local personal flight. Visual meteorological conditions prevailed at the time. No flight plan was filed for the operation. The aircraft incurred substantial damage. The certificated commercial pilot, the sole occupant, was seriously injured. The flight originated from Montgomery Field, San Diego, California, at approximately 1300 on the day of the mishap and had made a precautionary landing at Borrego Springs.

In a telephone interview, the pilot stated that he rented the aircraft to do some basic air work. After takeoff, he flew eastbound deciding to make some practice approaches at Borrego Springs airport. While enroute at 5,500 feet mean sea level, he noticed that the engine began running rough. He decided to make a precautionary full stop landing at Borrego Springs airport to see if he could determine the nature of the problem.

After landing, he taxied to the ramp and shut down the aircraft. At this time, he performed an inspection of the aircraft, but was unable to identify any problem. He discussed his problem with personnel at a fixed base operator on the field, and it was suggested to him that he possibly could have been experiencing some moisture in the fuel or carburetor icing. After this discussion, he decided to perform another run-up, thinking the problem could have been transient. On run-up, the engine developed 2,100 rpm's at full throttle. He determined that this was not sufficient power for takeoff.

He taxied back to the ramp, shut down, and called the aircraft operator to inform them of the situation and to request help in recovering the aircraft. He spoke with a woman whom he identified as one of the owners of the aircraft. The owner suggested that the problem could be a faulty cylinder, and told the pilot that she would drive or fly to Borrego Springs and fly the aircraft back herself if he did not feel comfortable in flying back himself. He told her that it had also been suggested that icing or moisture may have been the problem and she agreed that too was a possibility. He told her he would try another run-up and, if the performance improved, he would fly the aircraft back himself.

On the second run-up, engine rpm improved to the range of 2,200 to 2,300 rpm. The pilot said he felt that this was sufficient for the return flight and taxied for takeoff. The takeoff roll seemed slower than normal, and his decision was to climb to altitude above the airport so that he would be in a position to make an emergency landing if the problem worsened. He climbed straight out until reaching 100 to 200 feet above ground level, angling away from the runway centerline in the event he needed to make an immediate return to the airport. At that time, the engine began running rough and he began a shallow turn back toward the runway. Before reaching the runway, he determined that he did not have sufficient power to remain aloft and began looking for a place to land the aircraft. The pilot reported that, while still in a shallow turn, he lost control of the aircraft. The aircraft impacted the ground wing low and then nosed over onto its back.

After the aircraft was recovered, the wreckage was examined at an aircraft salvage yard. The inspection of the Continental O-200A engine, serial No. 61689-5-A, revealed the rocker arm boss on the No. 1 cylinder had fractured and separated. The surface of the center boss exhibited evidence of surface peening. The boss was fitted with bushings and also appeared to have been welded. The boss surface appeared to have been smoothed with a grinding wheel. The No. 4 cylinder boss also exhibited indications of having been welded.

The crankshaft was rotated without any indications of binding. A manual field compression check found movement and compression in all four cylinders when the crankshaft was rotated. The spark plugs from all four cylinders had black, sooty deposits. Both left and right magnetos produced electrical sparks when the crankshaft was rotated. The air filter grill was intact and undamaged. Both tips on the McCalley propeller were bent aft. There was no apparent leading or trailing edge damage.

The right and left fuel caps were inspected. The vents on both caps were clear and the seals were in good condition. There were only slight indications of fuel seepage around the right and left fuel drainage sumps. Both main wing fuel tank vents were clear. Approximately 5 gallons of fuel from the right tank and 10 gallons of fuel from the left tank were drained prior to recovery. The fuel was reported to have been blue in color.

The rocker arms, rocker shaft, bushings, and separated pieces of the three rocker shaft bosses from the cylinder head, all from the No. 1 cylinder assembly of the engine, were submitted to the Materials Laboratory Division of the National Transportation Safety Board for metallurgical analysis. The report concluded that the rocker boss failed due to fatigue cracking. A spectrum analysis of the surface of the center rocker boss revealed an alloyed metal consistent with welding. The engine manufacturer's overhaul procedures do not allow for any welding in the rocker boss area. The complete metallurgical laboratory report is attached.

A review of the aircraft's maintenance records by a Federal Aviation Administration airworthiness inspector failed to identify the rework facility responsible for the placing the No. 1 cylinder rocker boss in service.